Antibodies against rat basophilic leukemic cell membrane will be tested for the ability to release histamine from rat mast cells. The F(ab')2 and Fab fragments of the antibody will be tested for the activity. The presence of Fc receptors on human basophils and the relationship between Fc receptor and IgE receptor will be studied. Mechanisms of histamine release by anaphylatoxin, and the binding of C3a and C5a with human leukocytes will be studied. BIBLIOGRAPHIC REFERENCES: IgA and IgG anti-ragweed antibodies in nasal secretions. Quantitative measurements of antibodies and correlation with inhibition of histamine release. Platts-Mills, T.A., vonMaur, R.K., Ishizaka, K., Norman, P.S. and Lichtenstein, L.M. J. Clin. Invest., 57: 1041, 1976. Development of mast cells in vitro. II. Biologic function of cultures mast cells. Ishizaka, T., Adachi, T., Chang, T. and Ishizaka, K. J. Immunol., 118: 211, 1977.